Introduction to The Ascent Roadmap

The Ascent Roadmap is a product of the After Columbia Project (http://aftercolumbia.tripod.com/ and http://aftercolumbiamars.blogspot.com/). It is intended to chart the most economical booster concepts for each class of payload

The Ascent Roadmap is also a significant part of the OpenLuna Wiki (which will eventually begin to concentrate on the Lunar Access Plan.) The following is from memory, and should be very similar in jist to what you will find at http://www.openluna.org/wiki/index.php/Ascent_Roadmap but not verbatim.

First, I highly recommend the book by John R. London III, LEO On The Cheap hosted at http://www.dunnspace.com/. It has only one glitch, as does almost all advocates of Minimum Cost Design (MCD) boosters: it has underestimated the scaling problem of total thrust pressure, which makes it very difficult to design large pressure-fed boosters with payloads above 20 tonnes to Low Energy Orbit.

Payload Class Boosters:

Prochron: 3kg to Low Earth Orbit.
Earth-to-Orbit Centerpiece of: Hobby Access Plan (status=stub)
Stage One: off the shelf high power rocket motors of N impulse class. These motors provide the initial thrust to lift the booster out of the launch tower and give it enough speed so that it's passively stable design has enough speed to avoid excessive weathervaning. They are jettisoned after six seconds, and are recovered the same way as high power rockets are always (sic) recovered: parachute and puppy dog.
Stage Two (ver. 0811A): A core stage with fins, a single motor, oxyfuel (probably oxypropane) propellant combination. Additional stages, if applicable, are stacked on top. The entire assembled vehicle fits under a total impulse class of T, allowing it to be operated as an amateur rocket...as long as it stays under 150km peak altitude.
Stage Two (ver. 0811B): 3 common modules, the sort inspired by OTRAG, strapped to a core stage. Each module is a blowdown single motor stage (probably oxypropane). This means that Prochron amateur rockets could use this module, and possibly be far smaller than ver. 0811A.
Stage Three (ver. 0811A): a single common diameter stage stacked on top of the second stage core, with a small pressure-fed oxyfuel motor, smaller than that in Stage Two.
Stage Three (ver. 0811B): The single module in between the Stage Two modules, carrier of Stage Four (if applicable)
Stage Four: a small upper stage designed to apply a precise impulse bit to the payload to get it into the proper orbit and correct for errors in earlier stages. It carries a small cold gas RCS system.

Operation: Prochron flies passively (or semi-passively) through Stages One and Two, which operate in the atmosphere. Stages Three and Four require active guidance and stabilization to correct from Stages One and Two, and because without air, fins don't work. The fairing is jettisoned during Stage Three. The payload is based on CalPoly's Cubesat (http://www.cubesat.org/). 3kg forms a single "pod" of CubeSats.

Symtex: Up to 500kg to orbit
Earth-to-Orbit Centerpiece of: nothing so far
A modular pressure-fed launch vehicle intended to fill the niche underneath the Orbital Sciences Pegasus and Minotaur class boosters. If it entered service as a commercial launch vehicle, it would have no competition, except for the very largest configuration, which nearly matches Pegasus/Minotaur performance.

Common Motor: a single oxyfuel (probably oxypropane, possibly same as Prochron Stage Two ver. 0811A) used by all stages except for the upper stage, which mounts a smaller Space Motor (probably same as Prochron Stage Three).

Strap-on Module: Wide enough only to mount one Common Motor, this small module provides high lift-off thrust for about 40 seconds.

Core Modules: Mounts any number of motors from one to four (including the possibility of a single high expansion version for a second stage.) They will probably be cut to two different lengths. Try not to think of them as putty-like: stretching and cutting stages is not so simple.

Upper Stage: Contains the guidance system, is multiple maneuver capable, and contains the payload interface and vehicle electrical sources. A special type of internal gear expander coupled pump (think "displacement turbopump") is being considered. It is based on the StarRotor design (http://www.starrotor.com/), and StarRotor Corporation has been queried for its potential use. Special thanks to them for providing After Columbia Project with basic application formulae and the University of Idaho ALLPROPS software.

Operation: Symtex is actively guided all the way to orbit, but it is intended that it be passively stable until at least the first staging event. It therefore does not require a tower or rail for weathervaning control. For conventional launch vehicles, typically extensive balloons and often patrol aircraft are used to measure winds aloft. To avoid the expense, Symtex will provide extra margin for corrections, and extra thrust to get out of the atmosphere quickly, and thus mitigate the performance effects of wind shear. The smallest configurations use strap-configured core stages, who's core operates primarily as a second stage. The largest configurations will probably use Long Cores strapped by Short Cores, plus a final Short Core as a second stage. The upper stage will probably be used in such configurations for circularization maneuvers.

Kilder: 1000 to 8000kg Low Energy Orbit
Earth-to-Orbit Centerpiece of: Lunar Access Plan

Kilder features an pressure-fed oxyfuel (probably oxykerosene) core which must be strapped in order to rise from the pad. The strap-on system provides the first stage, and a squat, rotorpump engined (probably oxyethylene) upper stage comprises the third stage. The most advanced of the strap-on systems carry Lilmax turbopump engines, once that engine has been developed for Lilmax.

Lilmax: 15 to 50 tonnes Low Energy Orbit
Earth-to-Orbit Centerpiece of: Mars Access Plan
Lilmax begins to approach the size and complexity of typical boosters in terms of its systems and launch configurations, even though it is made of spun/rolled steel. Compared to extant boosters, it considers some very unusual features for its lower stage module, along with a more conventional upper stage. The modules come in a single length, without stretching or cutting down, however the upper stage will probably have two different sizes to accomodate different payload levels and final orbits. Unusual features (unusual both to "big dumb boosters" and conventional launch vehicles) are:
- Segmented tank construction: This allows rail and truck transportability of individual segments, which form a much larger stage when assembled. This is currently done with the Shuttle's solid boosters.
- Crossfeeding of propellants from strap-ons to core, allowing the core to remain full until the strap-ons burn out and are jettisoned.
- Pressure-stabilized structure. The normal tank pressure is 200psig with a burst factor of safety of 2.0, so it may be able to stand on its own anyway. If it can't, we'd rather use cradles and removable internal webs during transport than add stiffeners to the design. Most boosters are stiffened adequately to withstand handling loads without pressure, but require internal pressure to withstand flight loads; the SpaceX Falcon describes this as though it is unusual, but it is actually the normal case.
- Recoverable and Reusable: Whatever range Lilmax winds up with, at least the first set of strap-on modules will be reusable, even if they hit dry land. Dry land may be preferable because trucks are cheaper than ships.
- High tank pressure ensures simplified turbopump design, and large safety margins for flight loads and recovery.
- Modules will have a blowdown phase late during their operation (this is also normal for most boosters), what is different with Lilmax is that after shutdown (for recoverable modules only), the tank residuals boil off and rebuild pressure for recovery. During the blowdown phase, the engines are throttled back because less suction pressure is available for the turbopumps.

Bluestar: 8000kg LEO payload fully reusable booster and orbital service vehicle
Earth to Orbit Centerpiece of: Station Access Plan (status=stub), used to be International Space Transportation System
Bluestar has evolved considerably since I first drew it up in 2001. Since then, I have discovered that putting wings on spacecraft is about as silly as equipping submarines with screen doors and wings to allow them to fly through the air. The Space Shuttle suffers horrendous expense because its wings, control surfaces, hydraulics, and landing gear (including 100lb of tire air) are carried all the way to orbit and do absolutely nothing to add to the Shuttle's functionality in space. 60 tonnes of nothing more than ballast until less than half an hour before landing. 55% of the Shuttle's orbital mass is used only for the last 0.17% of a twelve day mission. At first, Bluestar was based on Saenger II and Ashford Spacebus (http://www.bristolspaceplanes.com/projects/spacebus.shtml ... from memory, yikes!) but is now based on Lilmax.

Bluestar now implements a ballistically recoverable upper stage for ascent on the Lilmax lower stage modules. For basic LEO (Low Energy Orbit) services, more than one variant may be required. The satellite payload version is described at http://www.openluna.org/wiki/index.php/Bluestar. A station logistics variant would better resemble the Sprint Crew Ferry (http://aftercolumbia.tripod.com/deltasprint/ where you will see why I lament not preserving Brian Heick's excellent 3D artwork of this concept in support of the Orbiter Mars Direct Project.) Inside such a ferry would be the racking one would normally see inside a Leonardo class module or a SpaceHab Logistics module.

Freezerburn: 100 tonnes and up
Centerpiece of: Mars Access Plan (Phase II)
The colonization of Mars, and possibly other destinations, will require cheap heavy lift services, a very challenging mission. Heavy lifters will also be required for space hotels, and in the unlikely event they should prove economical, solar power satellites.
- Basic Freezerburn core is formed by adding structural end pieces to four Lilmax modules. These four modules then form the basic Freezerburn core stage almost for free. This is not unprecedented at all: the Saturn IB stage was formed very similarly from eight Redstone tanks and one Jupiter tank.
- Up to 12 Lilmax modules can be strapped onto the core. At least four would normally be strapped onto the core, because with only the core, Freezerburn's capacity would not exceed that of the largest Lilmax configuration, which uses five modules.
- A very large, 9m diameter upper stage is used on Lilmax. It is not recoverable, but may be reusable by incorporating it into structures in space. The most likely propellant combination for this upper stage is oxymethane, or LOX/LNG (LNG being 16% ethane, 84% methane, with trace amounts of hydrogen sulphide and helium.)
- The most likely growth option is to extend the upper stage into a booster core which sits on top of the four module core already in place. On to this, Lilmax strap-on modules above their equivalents strapped to the first stage would be attached to the upper stage. Intermediate is to use the widebody core directly on the first stage with an older upper stage on top of it.

This concludes the Ascent Roadmap introduction!!